FIG. 1 shows a prior-art push bench 20 for manufacturing seamless pipes 1 from a tubular block 2. The figure also shows the manufacturing steps and the sequence thereof designated by arrows:
The tubular block 2 serves as the starting material. It is obtained, for example, by heating a solid block and piercing it by skew-rolling the block over a mandrel or pressing a piercing mandrel into it so that a passage 3 extends through the tubular block.
The tubular block 2 is then placed into a dishing press 10. It serves to compress together one end of the tubular block 2 such that a force-fit end 4 is formed for force-fitting to a mandrel rod 21 that is usually inserted into the undished tubular block or, alternatively, in the following step, into the passage 3 of the tubular block 2. The assembly of the tubular block 2 and the mandrel rod 21 is then introduced into the intake end of the push bench 20.
A drive apparatus 25 with a feeder 26 and a pusher rod 27 presses the mandrel rod 21 and the tubular block 2 forward through the push bench 20. For this purpose, the feeder 26 pushes the shaft rod 27 forward, and this, in turn, acts on a rear end 22 of the mandrel rod 21. The mandrel rod 21 and the tubular block 2 are driven forward together through a roller mill 30 by the force-fitted end 4 of the tubular block 2 produced previously in the dishing press 10, with the tubular block 2 acting on the front end 23 of the mandrel rod 21. The rollers in the push bench 20 are not driven. The tubular block 2 is thus rolled onto the mandrel rod 21 during the pushing process. A shaping, particularly an elongation, of the tubular block 2 takes place as can be seen from FIG. 1. The semifinished product manufactured in this way—the pipe 1—is also referred to in the technical field as a tubular.
After rolling-out the tubular block 2 to form the pipe 1, the drive apparatus 25 returns with the shaft rod 27 into the starting position. This causes the mandrel rod 21 and the shaft rod 27 located in the rolled pipe 1 to separate from one another. The push bench 20 is ready for the next rolling cycle.
Parallel to this, the rolled-out pipe 1 is pushed with the mandrel rod 21 into a detaching roller mill 40, also called a reeler, that serves to separate the pipe 1 and the mandrel rod 21 from each other. To this end, the diameter of the pipe 1 is enlarged by a rolling process between skew pairs of concave rollers, so that the pipe 1, which has shrunk onto the mandrel rod 21 as a result of the temperature loss, can be separated from the mandrel rod.
In an extractor 50, the mandrel rod 21 is then pulled rearward out of the pipe 1. At the same time, the pipe 1 is held back by a clamp 60. After that, the pipe 1 can be conveyed to other processing steps, such as for diameter and/or size reduction. The mandrel rod 21 is returned to the mandrel rod cycle.
Conventional system and method layouts are described in:                “Herstellung von Rohren” [“Manufacture of Pipes”], Verlag Stahleisen MbH, Düsseldorf, 1975, image 3, p. 16 and image 14, p. 26        Burkhard Schifferings, “Herstellverfahren für nahtlose Rohre mit kleiner and mittlerer Kapazität” [“Manufacturing methods for small- and medium-capacity seamless pipes”], Neue Hütte, volume 32, issue 1, 1987        
Additional methods and apparatuses also are seen in DE 1 452 255 and U.S. Pat. No. 2,819,790.
During separation of the pipe 1 from the mandrel rod 21, the pipe 1 is widened in the above-mentioned skew rolling process in the detaching mill 40 so that the mandrel rod 21 can be pulled out. This process results in deformation of the pipe 1, which can degrade the product quality. In particular, the danger exists of the wall thickness of the pipe 1 becoming irregular.
Moreover, the detaching mill 40 and the extractor 50 are system components that are made available as part of the push bench 20 or as separate system parts and must be configured and maintained in order to work together with the push bench 20. Furthermore, the system cannot do without technical means for transporting and circulating of the mandrel rods 21 between the individual stations.